/*

 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.nashorn.tools.jjs;

import java.io.IOException;

import java.nio.charset.Charset;

import java.nio.file.ClosedWatchServiceException;

import java.nio.file.FileSystems;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.WatchKey;

import java.nio.file.WatchService;

import java.util.List;

import java.util.function.Consumer;

import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE;

import static java.nio.file.StandardWatchEventKinds.ENTRY_DELETE;

import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY;

final class ExternalEditor {

    private final Consumer<String> errorHandler;

    private final Consumer<String> saveHandler;

    private final Console input;

    private WatchService watcher;

    private Thread watchedThread;

    private Path dir;

    private Path tmpfile;

    ExternalEditor(final Consumer<String> errorHandler, final Consumer<String> saveHandler, final Console input) {

        this.errorHandler = errorHandler;

        this.saveHandler = saveHandler;

        this.input = input;

    }

    private void edit(final String cmd, final String initialText) {

        try {

            setupWatch(initialText);

            launch(cmd);

        } catch (IOException ex) {

            errorHandler.accept(ex.getMessage());

        }

    }

    /**

     * Creates a WatchService and registers the given directory

     */

    private void setupWatch(final String initialText) throws IOException {

        this.watcher = FileSystems.getDefault().newWatchService();

        this.dir = Files.createTempDirectory("REPL");

        this.tmpfile = Files.createTempFile(dir, null, ".js");

        Files.write(tmpfile, initialText.getBytes(Charset.forName("UTF-8")));

        dir.register(watcher,

                ENTRY_CREATE,

                ENTRY_DELETE,

                ENTRY_MODIFY);

        watchedThread = new Thread(() -> {

            for (;;) {

                WatchKey key;

                try {

                    key = watcher.take();

                } catch (final ClosedWatchServiceException ex) {

                    break;

                } catch (final InterruptedException ex) {

                    continue; // tolerate an intrupt

                }

                if (!key.pollEvents().isEmpty()) {

                    if (!input.terminalEditorRunning()) {

                        saveFile();

                    }

                }

                boolean valid = key.reset();

                if (!valid) {

                    errorHandler.accept("Invalid key");

                    break;

                }

            }

        });

        watchedThread.start();

    }

    private void launch(final String cmd) throws IOException {

        ProcessBuilder pb = new ProcessBuilder(cmd, tmpfile.toString());

        pb = pb.inheritIO();

        try {

            input.suspend();

            Process process = pb.start();

            process.waitFor();

        } catch (final IOException ex) {

            errorHandler.accept("process IO failure: " + ex.getMessage());

        } catch (final InterruptedException ex) {

            errorHandler.accept("process interrupt: " + ex.getMessage());

        } finally {

            try {

                watcher.close();

                watchedThread.join(); //so that saveFile() is finished.

                saveFile();

            } catch (InterruptedException ex) {

                errorHandler.accept("process interrupt: " + ex.getMessage());

            } finally {

                input.resume();

            }

        }

    }

    private void saveFile() {

        List<String> lines;

        try {

            lines = Files.readAllLines(tmpfile);

        } catch (final IOException ex) {

            errorHandler.accept("Failure read edit file: " + ex.getMessage());

            return ;

        }

        StringBuilder sb = new StringBuilder();

        for (String ln : lines) {

            sb.append(ln);

            sb.append('\n');

        }

        saveHandler.accept(sb.toString());

    }

    static void edit(final String cmd, final Consumer<String> errorHandler, final String initialText,

            final Consumer<String> saveHandler, final Console input) {

        ExternalEditor ed = new ExternalEditor(errorHandler,  saveHandler, input);

        ed.edit(cmd, initialText);

    }

}